The present invention relates generally to flexible containers for housing liquid. More specifically, the present invention relates to containers that can be filled with a liquid under sterile conditions.
It is known to use flexible containers for housing parenteral and enteral solutions, such as liquid nutrients. Such containers should be manufactured and filled under sterile conditions to insure that they can be safely infused into patients.
In an article by I. M. Anderson entitled: Intasept --Aseptic Integrity in Bag-In-Box Packaging, Food Technology in Australia, Vol. 37 (9) September, 1985, pp. 399-401 a system is demonstrated for bag-in box packaging of liquids, and a machine for aseptic filling of such flexible, collapsible containers. As described in the article, a flexible, collapsible container, which comprises a pair of flexible plastic walls peripherally joined together, is filled through the use of a tubular port. The tubular port extends through one of the walls of the container to the container interior. The container includes spaced, outer and inner sealing diaphragms at either end of the tubular port. The outer diaphragm is outside of the walls of the container, and the inner diaphragm is inside the walls thereof.
The outer diaphragm is completely sealed to the tubular port about its periphery. But, the inner diaphragm is only spot sealed about its periphery so that fluid flow can take place across the inner diaphragm between the spot seals.
As described in the article, the flexible, collapsible container is connected to the Intasept filling machine. The outside of the tubular port is sterilized, and the container interior is typically already sterile. After sterilization, the outer membrane is penetrated, but not the inner membrane. The container is then filled through the tubular port with the desired amount of liquid, following which the inner membrane is welded in a continuous loop seal by welding which takes place through both walls of the container so that the container interior is sealed.
The disclosed bag system, and the method for filling and sealing it, has certain disadvantages. For example, a special laminated material must be used for the inner membrane, so that the inner membrane can be heat sealed to the tubular port, while the opposite container wall, through which the heat sealing process takes place, does not seal to the inner membrane. Additionally, the initial attachment of the intermittently sealed inner membrane is a matter of some complexity in the first place. Accordingly, the structure described in the Anderson article is difficult to make and costly.
U.S. Pat. No. 4,840,017, the disclosure of which is incorporated herein by reference, discloses a flexible, collapsible container that can be filled with conventional, aseptic filling machines, such as the Intasept machine, but which is a simpler structure, and which may be processed in a simpler manner to achieve the desired results of an aseptically sealed container for liquid materials with an improved seal.
To this end, the container comprises a pair of flexible plastic walls peripherally joined together. To fill the container, one connects a fluid conduit to a tubular port which communicates through one of the plastic walls to the container interior, thereby rupturing a sealed diaphragm that closes the bore of the tubular port. One then passes fluid through the conduit to fill the container, followed by sealing at least one wall of the tubular port and one plastic wall to the other plastic wall, forming a seal line that serves to close off flow communication between the tubular port and the portion of the container interior that contains the fluid. Thus, the container is sealed. In an embodiment, the seal line is a closed-loop seal that completely surrounds the bore to effectively block flow communications between the bore and the remaining portions of the container interior.
Although such a structure does provide a method for filling a container in a sterile manner, there may be disadvantages with such a container. In this regard, when the bore is sealed therearound by a closed-loop, after it has been filled with fluid, it has been found that the closed-loop seal acts as a stress concentrator. During shipping the container may fail due to the stresses that are exerted on the closed-loop seal.
A further problem that exacerbates the concentration of stress on the closed-loop seal is that the fact that the closed-loop seal is created after the container filling process. Therefore, residue such as oils from the liquid product that is housed in the container may still be on the interior of the flexible walls that are sealed together. This may result in a seal that cannot withstand the same stress that can be withstood by a seal created when the plastic is sealed in a dry state.